Schematic of sentinel node detection using ICG and OPUS, utilizing optoacoustic contrast of biomarkers in tissue using multispectral excitation. The contrast images are overlaid on tomographic ultrasound images, as well as using three dimensional optoacoustic detection. Credit: S. Morscher, I. Stoffels, J. Claussen, J. Klode
Scientists are testing a noninvasive alternative to lymph node biopsy for detecting early signs that melanoma skin cancer has spread. Patients currently undergo surgical removal, often involving a radioactive tracer, of these lymph nodes to screen for wayward cancer cells. But researchers say that in most cases this approach uncovers no sign of cancer spread while exposing patients to unnecessary risks. A team from Germany now reports that a new audio-visual imaging technique looks as effective as surgery for identifying melanoma metastasis.
Melanoma is the 5th most common cancer in the US, and the deadliest type of skin cancer. Survival odds are highest the earlier a diagnosis is made, before it spreads through the lymphatic system. When a patient diagnosed with melanoma is later found to have an enlarged lymph node, surgery follows. And even without lymph enlargement, high concern over the risk of melanoma spread can prompt pre-emptive surgery ie sentinel lymph node biopsy. “We obviously have to do this type of surgery in order to ‘stage’ the cancer,” said Assoc. Prof Weeraratna. “But only about a third of patients are actually found to have metastatic cancer,” said Weeraratna, who was not part of the study team.
“There is always some risk with surgery. For example, surgery can lead to nerve damage, especially in the facial head and neck area,” she added. Stoffels tested the potential of a nonradioactive and noninvasive diagnostic alternative: multispectral optoacoustic tomography (MSOT). It identifies melanin pigment naturally found in melanoma tumor cells. Clinicians inject green dye, instead of radioactive material, into the initial cancer site, and track its spread to the key sentinel lymph nodes. Then a handheld laser pulses light through the patient’s skin and into the nodes, where it generates an ultrasound signal. That signal is then analyzed for signs of melanin. No melanin means no cancer spread, and no surgery.
In a lab setting, MSOT was applied to over 500 lymph nodes surgically removed from 214 melanoma patients. The new technique outperformed the standard diagnostic approach at correctly identifying cancer spread. The technique was then applied to 20 melanoma patients who had not yet undergone surgery. The study found that MSOT accurately spotted every case of metastasis, and definitively ruled out cancer spread in almost half the patients, thereby sparing them surgery. A larger follow-up study to confirm the findings is planned. He added that the technology might also help identify metastasis in patients diagnosed with breast cancer or penile cancer.
“But now we need to make sure that in the long-run this approach actually translates into cancer survival rates that are as good as what we have with lymph node surgery.” http://medicalxpress.com/news/2015-12-scan-lymph-node-biopsy.html
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